Currents on Transmission of Excitation. 



489 



former, as stated before, will be designated as the homodromous, and the 

 latter as the heterodromous current. Electrical connections are so arranged 

 that when the commutator is tilted to the right, the current is homodromous 

 when tilted to the left, heterodromous. 



For the purpose of convenience I shall call the constant current the. 



Fig. 2. — Complete apparatus for investigation of the variation of conducting power in 

 Mimosa. A, storage cell ; S, potentiometer slide, which, by alternate movement to 

 right or left, continuously increases or decreases the applied E.M.F. ; K, switch key for 

 putting current " on " and " off" without variation of resistance ; E, E', electrodes of 

 induction coil for stimulation ; C, choking coil ; G, microammeter. 



polarising current, as it will be shown that its effect on conductivity is 

 discriminative or polar, depending on the direction of the current. It 

 should, however, be distinctly understood that under the particular experi- 

 mental arrangement the possibility of polar variation of excitability at the 

 points of stimulation and region of response is avoided. 



